1. Field of the Invention
The present invention relates generally to devices and methods for performing thoracoscopic cardiac procedures. More particularly, the present invention relates to devices and methods for performing coronary artery bypass graft (CABG) surgery for multivessel coronary artery disease through port-access or closed-chest thoracoscopic methods.
2. Background of the Invention
Coronary artery disease remains the leading cause of morbidity and mortality in Western societies. Coronary artery disease is manifested in a number of ways. For example, disease of the coronary arteries can lead to insufficient blood flow resulting in the discomfort and risks of angina and ischemia. In severe cases, acute blockage of coronary blood flow can result in myocardial infarction, leading to immediate death or damage to the myocardial tissue.
A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to treat the symptoms with pharmaceuticals and lifestyle modification to lessen the underlying causes of disease. In more severe cases, the coronary blockage(s) can often be treated endovascularly using techniques such as balloon angioplasty, atherectomy, laser ablation, stents, hot tip probes, and the like.
In cases where pharmaceutical treatment and/or endovascular approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft procedure using open surgical techniques. Such techniques require that the patient""s sternum be opened and the chest be spread apart to provide access to the heart. A source of arterial blood is then connected to a coronary artery downstream from an occlusion while the patient is maintained under cardioplegia and is supported by cardiopulmonary bypass. The source of blood is often the left or right internal mammary artery, and the target coronary artery can be the left anterior descending artery, circumflex artery, right coronary artery or any one of their branches which might be narrowed or occluded.
While very effective in many cases, the use of open surgery to perform coronary artery bypass grafting is highly traumatic to the patient. The procedure requires immediate postoperative care in an intensive care unit, a total period of hospitalization of seven to ten days, and a recovery period that can be as long as six to eight weeks.
It would therefore be desirable to provide other, less traumatic methods and techniques for performing coronary artery bypass grafting. It would be particularly desirable if such techniques did not require opening of the patient""s sternum, and might be even more desirable if such techniques could be performed using thoracoscopic methods. Such thoracoscopic methods could decrease morbidity and mortality, cost, and recovery time when compared to conventional open surgical coronary bypass procedures. In addition, such methods could be even more efficacious than open-surgical bypass procedures.
Copending U.S. patent application Ser. No. 08/281,891 describes a method of performing coronary bypass graft surgery for single vessel coronary artery disease using port-access or closed-chest thoracoscopic methods. However, of the over 365,000 open-chest CABG operations performed in 1993, only 5-15% were for single vessel coronary artery disease. For the benefits of thoracoscopic CABG surgery to reach the remainder of the patient population, the procedure must be expanded to address multivessel disease. Treatment of multivessel coronary artery disease involves rerouting multiple conduits to supply blood to the blocked coronary arteries downstream of the blockages. Typical conduits used for CABG surgery in multivessel disease include arterial conduits, such as the left internal mammary artery (LIMA), the right internal mammary artery (RIMA) or the right gastroepiploic artery (RGEA), or venous conduits such as the greater saphenous vein (GSV) or the lesser saphenous vein (LSV). Often a combination of these and other conduits is necessary to achieve complete revascularization of the obstructed coronary arteries. Open-chest approaches to treatment of multivessel coronary artery disease are described in Alternative Bypass Conduits and Methods for Surgical Coronary Revascularization, by Grooters and Nishida, Futura Publishing Company, Inc., Armonk, N.Y., 1994. Other references for standard open-chest methods of coronary artery bypass surgery include: Cardiac Surgery, by Kirklin and Barratt Boyes, John Wiley and Sons, Inc. New York, 1993 (2nd Ed.), and Rob and Smith""s Operative Surgery, Cardiac Surgery, The C V Mosby Co., St Louis, Mo., 1983 (4th Ed.).
A major challenge of thoracoscopic CABG surgery in multivessel disease is the ability to visualize and anastomose all of the coronary arteries through a limited number of access ports in order to minimize the trauma to the patient. This is made more difficult because many of preferred anastomosis sites on the branches of the right coronary artery and the circumflex artery are on the posterior aspect of the heart and therefore are difficult to access and to visualize with the heart in situ. Operating on the heart in situ would require separate access ports for the left coronary artery and each of the right coronary artery and the circumflex artery. Making this many access ports in the patient""s chest would undermine the atraumatic aspect of the thoracoscopic approach. In open-chest CABG surgery, this problem is solved by withdrawing the heart from the pericardial sac and manipulating it to expose the arteries on the posterior aspect. No instruments currently exist for manipulating the heart within the closed chest of the patient, making it difficult to duplicate the close-chest procedure with thoracoscopic techniques. Devices and methods are therefore necessary for manipulating the heart within the patient""s closed chest to expose each of the coronary arteries for visualization and anastomosis.
The additional length of time required for performing multiple anastomoses in multivessel CABG surgery also poses difficulties in terms of myocardial preservation during the lengthy procedure. In open procedures additional myocardial protection can be provided by topical hypothermia of the heart to reduce oxygen demand by the myocardium. The instruments and systems currently available for topical hypothermia in cardiac surgery are not suited for thoracoscopic techniques. New devices and methods are therefore necessary for cooling the heart within the patient""s closed chest to extend myocardial preservation during the multivessel CABG procedure.
The present invention describes devices and methods for performing port-access or closed-chest CABG surgery to treat multivessel coronary artery disease. All of the major steps of the port-access CABG procedure are performed through small percutaneous access ports to avoid the necessity of a median sternotomy or other gross thoracotomy, as required in prior open-chest approaches. The methods of the present invention include the steps of dissecting one or more conduit vessels, preferably arterial conduits, from their native locations, rerouting the conduit vessels to the heart and grafting the conduit vessels onto the blocked coronary arteries downstream of the blockages.
Generally, the step of dissecting the conduit vessels from their native locations or the xe2x80x9ctakedownxe2x80x9d is performed through small access ports using endoscopic visualization. In the case of a LIMA or RIMA takedown, the access ports are made into the patient""s thoracic cavity through the intercostal spaces and visualization is achieved using a flexible thoracoscope. Rerouting the LIMA involves redirecting the distal end of the LIMA to the desired anastomosis site. The RIMA may be rerouted anteriorly of the heart or it may be tunneled through the transverse sinus to reach the desired anastomosis site. In the case of an RGEA takedown, the access ports are made into the patient""s abdomen and visualization is achieved using a laparoscope. Rerouting the RGEA involves tunneling the distal end of the RGEA through a hole in the diaphragm to reach the desired anastomosis site on the heart. If venous grafts, such as the GSV, or other free grafts are used in place of or in addition to the arterial conduits, then the takedown or harvesting of the graft is performed by open or closed surgical techniques as appropriate and the graft is rerouted to the patient""s chest for anastomosis.
Specialized instruments for facilitating the takedown and rerouting steps are provided as part of the present invention. One instrument provided is a thoracoscopic tunneler for directing an arterial conduit through the transverse sinus or other tunneling path. One embodiment of a tunneler has an elongated shaft with a curved, rigid distal end with a hole through the distal tip for passing a tape or silastic tube through the transverse sinus to retract the pulmonary trunk to facilitate passage of the arterial conduit through the transverse sinus. Another embodiment of a tunneler has an elongated shaft with an articulated distal end with a grasper for reaching through the transverse sinus to grasp the arterial conduit and draw it through the transverse sinus to the desired anastomosis site. The two tunneling instruments may be used separately or in combination. In addition, a specialized thoracoscopic electrosurgical device may be provided to facilitate takedown of the arterial conduits. A suitable thoracoscopic electrosurgical device for this application is described in co-owned, copending patent application, Ser. No. 08/336,359, the entire disclosure of which is hereby incorporated by reference.
The step of grafting the conduit vessels onto the heart is accomplished under direct visualization using a cardioscopic microscope inserted through a visualization port into the patient""s thoracic cavity made through an intercostal space in the anterior wall of the chest. Additional surgical instruments are inserted through auxiliary ports into the patient""s thoracic cavity to perform the anastomosis of the conduit vessels to the coronary arteries. The devices. and methods of the present invention are devised to minimize the trauma to the patient by making it possible to visualize and access all aspects of the heart from a single centrally located visualization port by manipulating the heart within the patient""s closed chest with instruments inserted through the auxiliary access ports or through the takedown ports which remain from the takedown step. Generally, the distal end of each conduit vessel or graft is anastomosed to a coronary artery downstream of a blockage. Additionally, the conduit vessels may be sequentially grafted to more than one coronary artery or branch to form a xe2x80x9cskip graftxe2x80x9d. If free grafts are used an additional step of creating a proximal anastomosis must be performed. The proximal end of the graft may be anastomosed to the ascending aorta or to another of the conduit vessels to form a Y-graft. The step of making the proximal anastomosis may be performed before or after the distal anastomosis, depending on the preferences of the surgeon.
Specialized instruments are provided for manipulating the heart within the closed chest of the patient to rotate the desired anastomosis site into the visual field of the cardioscopic microscope. The specialized instruments include retractors which can manipulate the heart from outside of the body through one or more of the access ports. One embodiment of a retractor has an elongated shaft with a handle at the proximal end and a curved, finger-like manipulator at the distal end. The curved, finger-like manipulator may be covered with an absorbent and/or frictional material to improve its effectiveness at retracting, rotating and manipulating the heart. Another embodiment of a retractor has an elongated tubular shaft with a suction cup-shaped manipulator at the distal end. A vacuum is applied between the suction cup manipulator and the surface of the heart to grip the heart. The distal surface of the suction cup manipulator may have a textured or highly frictional surface to increase the grip on the surface of the heart, especially .in a direction tangential to the surface. The retractor can thus be used to retract or rotate the heart in any direction to expose the desired anastomosis site.
Another aspect of the present invention is to provide myocardial protection to the heart for the duration of the surgical procedure. A first component of the myocardial protection is to provide a means for establishing cardiopulmonary bypass (CPB) without the need for performing a thoracotomy or other grossly invasive procedure. One noninvasive method of establishing CPB involves the insertion of an endoaortic occlusion catheter into the ascending aorta through a percutaneous puncture into a peripheral artery. An inflatable occlusion balloon on the distal end of the catheter is used to partition the ascending aorta between the coronary ostia and the brachiocephalic artery to isolate the heart and coronary arteries from the remainder of the arterial system while it is supported on cardiopulmonary bypass. Cardioplegic solution to temporarily stop the heart from beating may be infused into the coronary arteries through the catheter and/or through a retroperfusion catheter percutaneously inserted in the coronary sinus. This method is more completely described in co-owned, copending patent application, Ser. No. 08/281,891.
Another relatively noninvasive method of establishing CPB involves using a thoracoscopic cross-clamp to isolate the heart and coronary arteries from the remainder of the arterial system while it is supported on cardiopulmonary bypass. The thoracoscopic cross-clamp is inserted into the patient""s thoracic cavity through an access port. Co-owned, copending patent application, Ser. No. 08/173,899, the entire disclosure of which is hereby incorporated by reference, describes a specialized thoracoscopic cross-clamp suitable use with the present invention and a method of its use for isolating the heart and establishing CPB.
A second component of the myocardial protection is to provide a means for applying topical hypothermia to the heart to reduce oxygen demand by the myocardium while the patient is on cardiopulmonary bypass and particularly while the heart is under cardioplegic arrest. A specialized topical hypothermia system that can be applied thoracoscopically through small access ports into the chest is provided as part of the present invention. The topical hypothermia system includes a flexible heat exchanger which is collapsible to fit through an access cannula inserted into an intercostal space. The heat exchanger is deployable to an expanded position once it is inside of the thoracic cavity. The heat exchanger is placed in thermal contact with the heart and a cooling fluid is circulated from outside the body through cooling passages within the heat exchanger. The temperature of the heart can be lowered for the duration of the procedure to reduce oxygen demand. The heat exchanger can also be used for warming the heart at the end of the procedure by circulating a warm fluid through the cooling passages.